Polycarbonate production method

ABSTRACT

Polycarbonates are prepared by inducing the melt polycondensation of an aromatic dihydroxy compound and a diester carbonate in the presence of alkali metal compounds and/or alkaline earth metal compound droxy and adding to the polycarbonate which is the reaction product thereof: a sulfonic acid compound having the formula ##STR1## in an amount to 0.05-10 ppm, based on the polycarbonate, and also an epoxy compound in an amount of 1-2000 ppm, based on the polycarbonate.

This is a divisional of co-pending application Ser. No. 07/903,320 filedon Jun. 24, 1992, now U.S. Pat. No. 5,306,801.

[DETAILED DESCRIPTION OF THE INVENTION] [Field of the Invention]

The present invention relates to a polycarbonate production method. Morespecifically, it relates to a polycarbonate production method that iscapable of preparing polycarbonates which have excellent residencestability such as hue stability and heat stability at the time ofmolding, and which have particularly outstanding water resistance.

[TECHNICAL BACKGROUND OF THE INVENTION]

Polycarbonates have excellent mechanical properties such as impactresistance, as well as excellent heat resistance, transparency and otherproperties. They are widely used in applications such as various typesof mechanical components, optical disks, and automotive parts.

Polycarbonates such as these have hitherto been prepared by a methodinvolving the direct reaction of an aromatic dihydroxy compound such asbispherol A with phosgene (interfacial process) or a method involvingthe transesterification of an aromatic dihydroxy compound and a diestercarbonate (melt process).

Of these two methods, the melt process has the advantage of being ableto prepare polycarbonates more inexpensively than the interfacialprocess. Moreover, because it does not use toxic substances such asphosgene, it is also desirable from the standpoint of environmentalhealth.

In polycarbonate production methods by prior-art melt processes, alkalimetal compounds, alkaline earth metal compounds or the like aregenerally used as the catalyst in an amount of 10⁻³ to 10⁻⁶ mole permole of the aromatic dihydroxy compound.

However, polycarbonates obtained using an amount of catalyst such asthis have a poor residence stability. That is, when the polycarbonate ismelt-molded, some of it will at times undergo thermal decomposition, adecline in molecular weight, discoloration, and a decrease intransparency.

For example, Japanese Published Examined Patent Application [Kokoku] No.54-44,303 (1979) discloses a method for obtaining polycarbonates thatprevents a decline in the molecular weight at the time of molding. Thismethod involves carrying out a polycondensation reaction using an amountof 3.7×10⁻⁶ mole of the sodium salt of bisphenol A as the catalyst permole of the bisphenol A serving as the reactive monomer, and addingmethyl benzenesulfonate to the polycarbonate thus obtained. However, thepolycarbonate obtained by the method cited in this Kokoku has a poorinitial color tone, readily undergoes yellowing at the time of meltmolding, and tends to have an inferior heat resistance. Moreover, thewater resistance is not enhanced, hydrolysis readily arises, and thereis a tendency for the transparency to decrease.

Hence, the appearance of a method for preparing polycarbonates that isable to stably prepare polycarbonates having excellent residencestability such as hue stability and heat stability at the time of meltmolding, as well as excellent water resistance and transparency, hasbeen awaited.

The inventors conducted research on such polycarbonate productionmethods, as a result of which they found that by making alkali metalcompounds and/or alkaline earth metal compounds present in a specificamount within the polycondensation reaction system and by adding aspecific sulfonic acid compound to the polycarbonate obtained,polycarbonates can be prepared which have excellent residence stabilitysuch as hue stability and heat stability at the time of melt molding,and in particular excellent water resistance and transparency.

[OBJECT OF THE INVENTION]

The present invention was conceived in light of the above-describedprior art. Its object is to provide a polycarbonate production methodthat is capable of preparing polycarbonates which have excellentresidence stability such as hue stability and heat stability at the timeof melt molding, and in particular excellent water resistance andtransparency.

[GIST OF THE INVENTION]

The polycarbonate production method according to the present inventionis characterized by inducing the melt polycondensation of an aromaticdihydroxy compound and a diester carbonate in the presence of a totalamount in the reaction system of 5×10⁻⁸ to 8×10⁻⁷ mole of (a) alkalimetal compounds and/or alkaline earth metal compounds per mole of thearomatic dihydroxy compound, then adding to

[A] the polycarbonate which is the reaction product thereof:

[B] a sulfonic acid compound having formula [III] below in an amount of0.05-10 ppm, based on the polycarbonate. ##STR2## [where R⁷ is ahydrocarbon group having 1-6 carbons (in which the hydrogens may besubstituted with halogens), R⁸ is a hydrocarbon group with 1-8 carbons(in which the hydrogens may be substituted with halogens), and n is aninteger from 0 to 3].

In the polycarbonate production method according to the presentinvention, along with [B] the sulfonic acid compound, it is desirable toadd also:

[C] an epoxy compound in an amount of 1-2000 ppm, based on thepolycarbonate, and also

[D] a phosphorus compound in an amount of 10-1000 ppm, based on thepolycarbonate.

In the polycarbonate production method according to the presentinvention, the above (a) alkali metal compounds and/or alkaline earthmetal compounds should be added in an amount such that the total amountin the reaction system becomes 1×10⁻⁷ to 7×10⁻⁷ mole, and preferably1×10⁻⁷ to 6×10⁻⁷ mole, per mole of the aromatic dihydroxy compound.

In the present invention, because polycondensation is carried out bymaking a given amount of (a) alkali metal compounds and/or alkalineearth metal compounds present in the reaction system and because a givenspecific sulfonic acid compound [B] is added to the polycarbonate [A]obtained as the reaction product, the polycondensation reaction ismaintained at a high polycondensation activity, in addition to which theresulting polycarbonate has an excellent initial color tone immediatelyafter polycondensation, an enhanced residence stability and waterresistance, and also an excellent heat stability.

In the polycarbonate production method according to the presentinvention, polycarbonates having even further enhanced water resistancesand hue stabilities can be obtained by also adding [C] an epoxy compoundand [D] a phosphorus compound along with the sulfonic acid compound [B].

The polycarbonates obtained in the present invention are able to formmoldings having excellent residence stability at the time of meltmolding, low discoloration and, in particular, excellent waterresistance and transparency.

[CONCRETE DESCRIPTION OF THE INVENTION]

The polycarbonate production method according to the present inventionshall now be described more concretely.

In this invention, first a polycarbonate is prepared by inducing themelt polycondensation of an aromatic dihydroxy compound and a diestercarbonate in the presence of a catalyst.

There is no particular restriction on the aromatic dihydroxy compound,but compounds indicated by formula (II) below can be cited as examplesof these compounds. ##STR3## R¹ and R² are hydrogen atoms or monovalenthydrocarbon groups; R³ is a divalent hydrocarbon group; R⁴ and R⁵, whichmay the same or different, are halogens or monovalent hydrocarbongroups; and p and q are integers from 0 to 4).

Specific examples that may be cited of the above aromatic dihydroxycompounds include the following compounds: bis(hydroxyaryl)alkanes suchas bis(4-hydroxyphenyl)methane, 1,1-bis(4-hydroxyphenyl)ethane,2,2-bis(4-hydroxyphenyl)propane, 2,2-bis(4-hydroxyphenyl)butane,2,2-bis(4-hydroxyphenyl)octane, bis(4-hydroxyphenyl)phenylmethane,2,2-bis(4-hydroxy-1-methylphenyl)propane,1,1-bis(4-hydroxy-t-butylphenyl)propane and2,2-bis(4-hydroxy-3-bromophenyl)propane; bis(hydroxyaryl)cycloalkanessuch as 1,1-bis(hydroxyphenyl)cyclopentane and1,1-bis(4-hydroxyphenyl)cyclohexane; dihydroxyaryl ethers such as4,4'-dihydroxydiphenyl ether and 4,4'-dihydroxy-3,3'-dimethylphenylether; dihydroxydiarylsulfides such as 4,4'-dihydroxydiphenylsulfide and4,4'-dihydroxy-3,3'-dimethyldiphenylsulfide; dihydroxydiarylsulfoxidessuch as 4,4'-dihydroxydiphenylsulfoxide and4,4'-dihydroxy-3,3'-dimethyldiphenylsulfoxide; anddihydroxydiarylsulfones such as 4,4'-dihydroxydiphenylsulfone and4,4'-dihydroxy-3,3'-dimethyldiphenylsulfone.

Of these, the use of 2,2-bis(4-hydroxyphenyl)propane is especiallydesirable.

Compounds having formula [II] [sic] below can be used as the aromaticdihydroxy compound. ##STR4##

In the above formula, R₆ in each case represents hydrocarbon groupshaving 1-10 carbons, their halides, or halogens; each of these being thesame or different; and n is an integer from 0 to 4.

Specific examples that may be cited of the aromatic dihydroxy compoundsrepresented by formula [II] include substituted resorcinols such asresorcinol, 3-methylresorcinol, 3-ethylresorcinol, 3-propylresorcinol,3-butylresorcinol, 3-t-butylresorcinol, 3-phenylresorcinol,3-cumylresorcinol, 2,3,4,6-tetrafluororesorcinol and2,3,4,6-tetrabromoresorcinol; catechol; and substituted hydroquinonessuch as hydroquinone, 3-methylhydroquinone, 3-ethylhydroquinone,3-propylhydroquinone, 3-butylhydroquinone, 3-t-butylhydroquinone,3-phenylhydroquinone, 3-cumylhydroquinone,2,3,5,6-tetramethylhydroquinone, 2,3,5,6-tetra-t-butylhydroquinone,2,3,5,6-tetrafluorohydroquinone and 2,3,5,6-tetrabromohydroquinone.

The2,2,2',2'-tetrahydro-3,3,3',3'-tetramethyl-1,1'-spirobi-[IH-indene]-6,6'-diolrepresented by the following formula can also be used as the aromaticdihydroxy compound in the present invention. ##STR5##

These aromatic dihydroxy compounds can be used alone or as combinationsthereof.

Specific examples that may be cited of the diester carbonate includediphenyl carbonate, ditolyl carbonate, bis(chlorophenyl) carbonate,m-cresyl carbonate, dinaphthyl carbonate, bis(diphenyl) carbonate,diethyl carbonate, dimethyl carbonate, dibutyl carbonate anddicyclohexyl carbonate.

Of these, the use of diphenyl carbonate is especially desirable.

These diester carbonates can be used alone or as combinations thereof.

The above-cited diester carbonates may include preferably no more than50 mol %, and most preferably no more than 30 mol %, of dicarboxylicacids or dicarboxylates.

Examples that may be cited of these dicarboxylic acids or dicarboxylatesinclude aromatic dicarboxylic acids [and esters] such as terephthalicacid, isophthalic acid, diphenyl terephthalate and diphenylisophthalate; aliphatic dicarboxylic acids [and esters] such as succinicacid, glutaric acid, adipic acid, pimelic acid, suberic acid, azelaicacid, sebacic acid, decanedioic acid, dodecanedioic acid, diphenylsebacate, diphenyl decanedioate and diphenyl dodecanedioate; andalicyclic dicarboxylic acids [and esters] such ascyclopropanedicarboxylic acid, 1,2-cyclobutanedicarboxylic acid,1,3-cyclobutanedicarboxylic acid, 1,2-cyclopentanedicarboxylic acid,1,3-cyclopentanedicarboxylic acid, 1,2-cyclohexanedicarboxylic acid,1,3-cyclohexanedicarboxylic acid, 1,4-cyclohexanedicarboxylic acid,diphenyl cyclopropanedicarboxylate, diphenyl1,2-cyclobutanedicarboxylate, diphenyl 1,3-cyclobutanedicarboxylate,diphenyl 1,2-cyclopentanedicarboxylate, diphenyl1,3-cyclopentanedicarboxylate, diphenyl 1,2-cyclohexanedicarboxylate,diphenyl 1,3-cyclohexanedicarboxylate and diphenyl1,4-cyclohexanedicarboxylate.

Dicarboxylic acids or dicarboxylates such as these may be included aloneor as combinations thereof.

It is desirable that the above-cited diester carbonates generally beused in an amount of 1.0-1.30 moles, and preferably 1.01-1.20 moles, permole of aromatic dihydroxy compound.

In this invention, when preparing the polycarbonate, a polyfunctionalcompound having three or more functional groups per molecule may be usedalong with the above-cited aromatic dihydroxy compound and diestercarbonate.

These polyfunctional compounds are preferably compounds having phenolichydroxyl groups or carboxyl groups, with compounds having three phenolichydroxyl groups being especially desirable. Specific examples that maybe cited include 1,1,1-tris(4-hydroxyphenyl)ethane,2,2',2"-tris(4-hydroxyphenyl)diisopropylbenzene,α-methyl-α,α',α'-tris(4-hydroxyphenyl)-1,4-diethylbenzene,α,α',α"-tris(4-hydroxyphenyl)-1,3,5-triisopropylbenzene, fluoroglycine,4,6-dimethyl-2,4,6-tri(4-hydroxyphenyl)heptane-2,1,3,5-tri(4-hydroxyphenyl)benzene,2,2-bis-[4,4-(4,4'-dihydroxyphenyl)cyclohexyl]propane, trimellitic acid,1,3,5-benzenetricarboxylic acid and pyromellitic acid.

Of these, the use of 1,1,1-tris(4-hydroxyphenyl)ethane,α,α',α"-tris(4-hydroxyphenyl)-1,3,5-triisopropylbenzene or the like ispreferable.

The polyfunctional compounds are generally used in an amount of no morethan 0.03 mole, preferably 0.001-0.02 mole, and most preferably0.001-0.01 mole, per mole of the aromatic dihydroxy compound.

In the present invention, the above-described aromatic dihydroxycompound and diester carbonate are melt-polycondensed in the presence ofa catalyst consisting of (a) alkali metal compounds and/or alkalineearth metal compounds.

Preferable examples that may be cited of alkali metal compounds andalkaline earth metal compounds that can be used as the catalyst includethe organic acid salts, inorganic acid salts, oxides, hydroxides,hydrides and alcoholates of alkali metals and alkaline earth metals.

Specific examples of such alkali metal compounds include sodiumhydroxide, potassium hydroxide, lithium hydroxide, sodium bicarbonate,potassium bicarbonate, lithium bicarbonate, sodium carbonate, potassiumcarbonate, lithium carbonate, sodium acetate, potassium acetate, lithiumacetate, sodium stearate, potassium stearate, lithium stearate, sodiumboron hydride, lithium boron hydride, sodium boron phenylate, sodiumbenzoate, potassium benzoate, lithium benzoate, disodium hydrogenphosphate, dipotassium hydrogen phosphate, dilithium hydrogen phosphate,the disodium, dipotassium and dilithium salts of bisphenol A, and thesodium, potassium and lithium salts of phenol.

Specific examples of such alkaline earth metal compounds that may becited include calcium hydroxide, barium hydroxide, magnesium hydroxide,strontium hydroxide, calcium hydrogen carbonate, barium hydrogencarbonate, magnesium hydrogen carbonate, strontium hydrogen carbonate,calcium carbonate, barium carbonate, magnesium carbonate, strontiumcarbonate, calcium acetate, barium acetate, magnesium acetate, strontiumacetate, calcium stearate, barium stearate, magnesium stearate andstrontium stearate.

These compounds may be used alone or as combinations thereof.

These (a) alkali metal compounds and/or alkaline earth metal compoundsare used in an amount of 5×10⁻⁸ to 8×10⁻⁷ mole, preferably 1×10⁻⁷ to7×10⁻⁷ mole, and most preferably 1×10⁻⁷ to 6×10⁻⁷ mole, per mole of thearomatic dihydroxy compound.

The following should be done in order to use the (a) alkali metalcompounds and/or alkaline earth metal compounds in the above-describedamount and to make these present as catalysts in the overall reactionsystem.

The amount of alkali metal or alkaline earth metal impurities containedwithin the various components--such as the aromatic dihydroxy compound,the diester carbonate, and the nitrogen-containing basic compounds (b)described later-that are fed into the reaction system, excluding thealkali metal compounds and alkaline earth metal compounds (a), should bean amount that does not have an influence on the above amount ofcatalyst; for example, this should be no more than 1 ppb, in terms ofmetal equivalent.

In the event that these components contain a greater amount of metal oralkaline earth metal impurities than this, it is preferable that they befed to the reaction system after being purified so as to bring the levelof impurities within the respective components to 1 ppb or less, andthat the alkali metal compounds and alkaline earth metal compounds (a)be added at the time of the polycondensation reaction.

In the present invention, the alkali metal compounds and alkaline earthmetal compounds (a) serving as the catalyst are used in smaller amountsthan in the prior art, and are made present in a limited amount in theoverall reaction system.

In reaction systems in which this type of catalyst is present in aspecific small amount, polycarbonate can be produced while maintaining ahigh polymerization activity and under constant polymerizationconditions; yet, at the same time, a specific small amount of alkalinecompounds becomes present in the resulting polycarbonate. Hence,discoloration of the reaction product during the reaction is diminished,and polycarbonates having an excellent initial color tone immediatelyafter polycondensation can be obtained. Furthermore, polycarbonates canbe produced that have excellent residence stability such as heatstability and hue stability, and have an especially outstanding waterresistance.

In this invention, along with the above-described (a) alkali metalcompound and/or alkaline earth metal compound, it is also possible touse (b) a basic compound as the catalyst.

This basic compound (b) may be, for example, a nitrogen-containing basiccompound that readily decomposes or volatilizes at high temperatures.Specific examples that may be cited include the following compounds.

Ammonium hydroxides having alkyl, aryl, or aralkyl groups, such astetramethylammonium hydroxide (Me₄ NOH), tetraethylammonium hydroxide(Et₄ NOH), tetrabutylammonium hydroxide (Bu₄ NOH) andtrimethylbenzylammonium hydroxide (φ-CH₂ (Me)₃ NOH); tertiary aminessuch as trimethylamine, triethylamine, dimethylbenzylamine andtriphenylamine; secondary amines having the formula R₂ NH (where R is analkyl such as methyl or ethyl, an aryl group such as phenyl or toluyl,or the like); primary amines having the formula RNH₂ (where R is thesame as above); imidazoles such as 2-methylimidazole and2-phenylimidazole; and basic salts such as ammonia, tetramethylammoniumborohydride (Me₄ NBH₄), tetrabutylammonium borohydride (Bu₄ NBH₄),tetrabutylammonium tetraphenyl borate (Bu₄ NBPh₄) andtetramethylammonium tetraphenylborate (Me₄ NBPh₄).

Of these, preferable use can be made of tetralkylammonium hydroxides,and especially low-metal-impurity tetraalkylammonium hydroxides intendedfor electronics applications.

When nitrogen-containing basic compounds (b) such as those cited aboveare used as the catalyst, the nitrogen-containing basic compounds (b)are used in an amount of 10⁻⁶ to 10⁻¹ mole or less, and preferably 10⁻⁵to 10⁻² mole, per mole of the aromatic dihydroxy compound.

In addition, (c) boric acid compounds can be used as the catalyst.

Examples that may be cited of such boric acid compounds (c) includeboric acid and borates.

Examples that may cited of the borates include those borates having thefollowing formula.

    B(OR).sub.n (OH).sub.3-n

where R is an alkyl such as methyl or ethyl, or an aryl such as phenyl;and n is 1, 2 or 3.

Specific examples that may be cited of borates such as these includetrimethylborate, triethyl borate, tributyl borate, trihexyl borate,triheptyl borate, triphenyl borate, tritolyl borate and trinaphthylborate.

When boric acid or a borate (c) is used, this is used in an amount of10⁻⁸ to 10⁻¹ mole, preferably 10⁻⁷ to 10⁻² mole, and most preferably10⁻⁶ to 10⁻⁴ mole, per mole of the aromatic dihydroxy compound.

Preferable use of these as the catalyst can be made by combining, forexample,

(a) alkali metal compounds and/or alkaline earth metal compounds, and

(b) nitrogen-containing basic compounds, or by combining

(a) alkali metal compounds and/or alkaline earth metal compounds,

(b) nitrogen-containing basic compounds, and

(c) boric acid or borates.

Thus, catalyst consisting of a combination of (a) alkali metal compoundsand/or alkaline earth metal compounds, and (b) nitrogen-containing basiccompounds causes the polycondensation reaction to proceed at asufficient rate, making it possible to prepare high-molecular-weightpolycarbonate at a high polymerization activity.

Polycondensation reactions between the aromatic dihydroxy compound andthe diester carbonate in the presence of a catalyst such as this can becarried out under the same conditions as the polycondensation reactionconditions hitherto known to the art.

Specifically, in the step one reaction, the aromatic dihydroxy compoundand the diester carbonate are reacted at normal pressure, a temperatureof 80°-250° C., preferably 100°-230° C., and most preferably 120°-190°C., and for 0-5 hours, preferably 0-4 hours, and most preferably 0-3hours. Next, the reaction temperature is raised and the reaction betweenthe aromatic dihydroxy compound and the diester carbonate is carried outwhile placing the reaction system under a vacuum; polycondensationbetween the aromatic dihydroxy com-pound and the diester carbonate isultimately carried out under a vacuum of 5 mmHg or less, and preferably1 mmHg or less, and at 240°-320° C.

The polycondensation reaction described above may be carried out as acontinuous process or as a batch-type process. The reaction apparatusused when carrying out the above reaction may be a tank-type, tube-type,or column-type apparatus.

The polycarbonate reaction product obtained in the above mannergenerally has an intrinsic viscosity, as measured in 20° C. methylenechloride, of 0.10-1.0 dL/g, and preferably 0.30-0.65 dL/g.

As described above, production methods according to the presentinvention are desirable from the standpoint of environmental healthbecause they do not use toxic substances such as phosgene or methylenechloride in melt polycondensation.

In the present invention, sulfonic acid compounds [B] having formula[III] below are added to the polycarbonate [A] reaction product obtainedin the above manner. ##STR6## where R⁷ is a hydrocarbon group with 1-6carbons (in which the hydrogens may be substituted with halogens), R⁸ isa hydrogen or a hydrocarbon group with 1-8 carbons (in which thehydrogens may be substituted with halogens), and n is an integer from 0to 3, and preferably 0 or 1.

Examples that may be cited of sulfonic acid compounds [B] represented byformula [III] include the following compounds: sulfonic acids such asbenzenesulfonic acid and p-toluenesulfonic acid; sulfonates such asmethyl benzenesulfonate, ethyl benzenesulfonate, butyl benzenesulfonate,octyl benzenesulfonate, phenyl benzenesulfonate, methylp-toluenesulfonate, ethyl p-toluenesulfonate, butyl p-toluenesulfonate,octyl p-toluenesulfonate and phenyl p-toluenesulfonate,

Sulfonic acid compounds such as trifluoromethanesulfonic acid,naphthalenesulfonic acid, sulfonated polystyrene and methylacrylate-styrene sulfonate copolymers may also be used.

These compounds can be used alone or as combinations thereof.

In the present invention, preferable use can be made of those sulfonicacid compound [B] having formula [III] in which R⁷ is a methyl group, R⁸is an aliphatic hydrocarbon group having 1-6 carbons, and n is integer 0or 1. More specifically, the use of p-toluenesulfonic acid or butylp-toluenesulfonate is preferable.

In the present invention, the sulfonic acid compound [B] represented byformula [III] is added in an amount of 0.05-10 ppm, preferably 0.1-5ppm, and most preferably 0.2-2 ppm, based on the above polycarbonate[A].

The alkaline metal compound remaining in the polycarbonate 8 A] isneutralized or weakened by the addition of a specific sulfonic acidcompound [B] to the polycarbonate reaction product [A], ultimatelymaking it possible to obtain polycarbonate having an even more enhancedresidence stability and water resistance.

In polycarbonate production methods according to the present invention,it is preferable to add epoxy compounds [C] together with the sulfonicacid compounds [B] described above.

Compounds having one or more epoxy group per molecule can be used asthese epoxy compounds [C].

Specific examples that may be cited of epoxy compounds such as theseinclude epoxidized soybean oil, epoxidized linseed oil, phenylglycidylether, allylglycidyl ether, t-butylphenylglycidyl ether,3,4-epoxycyclohexylmethyl-3',4'-epoxycyclohexylcarboxylate,3,4-epoxy-6-methylcyclohexylmethyl-3',4'-epoxy-6'-methylcyclohexylcarboxylate,2,3-epoxycyclohexylmethyl-3',4'-epoxycyclohexylcarboxylate,4-(3,4-epoxy-5-methylcyclohexyl)butyl-3',4'-epoxycyclohexylcarboxylate,3,4-epoxycyclohexylethylene oxide,cyclohexylmethyl-3,4epoxycyclohexylcarboxylate,3,4-epoxy-6-methylcyclehexylmethyl-6'-methylcyclohexylcarboxylate,bisphenol A diglycidyl ether, tetrabromobisphenol A glycidyl ether, thediglycidyl ester of phthalic acid, the diglycidyl ester ofhexahydrophthalic acid, bis-epoxydicyclopentadienyl ether,bis-epoxyethylene glycol, bis-epoxycyclehexyl adipate, butadienediepoxide, tetraphenylethylene epoxide, octyl epoxyphthalate, epoxidizedpolybutadiene, 3,4-dimethyl-1,2-epoxycyclohexane,3,5-dimethyl-1,2-epoxycyclohexane,3-methyl-5-t-butyl-1,2-epoxycylehexane,octadecyl-2,2-dimethyl-3,4-epoxycyclohexylcarboxylate,N-butyl-2,2-dimethyl-3,4-epoxycyclohexylcarboxylate, cyclohexyl-2-methyl-3,4-epoxycyclohexylcarboxylate,N-butyl-2-isopropyl-3,4-epoxy-5-methylcyclohexylcarboxylate,octadecyl-3,4-epoxycyclohexylcarboxylate,2-ethylhexyl-3',4'-epoxycyclohexylcarboxylate,4,6-dimethyl-2,3-epoxycyclohexyl-3',4'-epoxycyclohexylcarboxylate,4,5-epoxytetrahydrophthalic anhydride,3-t-butyl-4,5-epoxytetrahydrophthalic anhydride,diethyl-4,5-epoxy-cis-1,2-cyclohexyldicarboxylate anddi-n-butyl-3-t-butyl-4,5-epoxy-cis-1,2-cyclohexyldicarboxylate.

Of these, the use of alicyclic epoxy compounds preferable, with the useof 3,4-epoxycyclohexylmethyl-3',4'-epoxycyclohexylcarboxylate beingespecially preferable.

These may be used alone or as mixtures of two or more thereof.

In the present invention, this type of epoxy compound [C] should beadded in an amount of 1-2000 ppm, and preferably 10-1000 ppm, based onthe above polycarbonate.

When this kind of epoxy compound [C] is added in the above amount, evenif an excess of the above sulfonic acid compound [B] remains presentwithin the polycarbonate [A], it reacts with the epoxy compound [C] andis thereby neutralized, enabling polycarbonate having an improved waterresistance to be obtained.

In the polycarbonate production method according to the presentinvention, a phosphorus compound [D] may be added along with thesulfonic acid compound [B].

Examples of compounds that may be used as these phosphorus compounds [D]include phosphoric acid, phosphorous acid, hypophosphorous acid,pyrophosphoric acid, polyphosphoric acid, phosphates, and phosphites.

Specific examples that may be cited of phosphates such as these includetrialkylphosphates such as trimethylphosphate, triethylphosphate,tributylphosphate, trioctylphosphate, tridecylphosphate,trioctadecylphosphate, distearylpentaerythrityldiphosphate,tris(2-chloroethyl)phosphate and tris(2,3-dichloropropyl)phosphate;tricycloroalkylphosphates such as tricyclohexylphosphate; andtriarylphosphates such as triphenylphosphate, tricresylphosphate,tris(nonylphenyl)phosphate and 2-ethylphenyldiphenylphosphate.

Examples that may be cited of phosphites include those compounds havingthe following formula

    P(OR).sub.3

(where R is an allcyclic hydrocarbon group, an aliphatic hydrocarbongroup or an aromatic hydrocarbon group; the groups represented by R maybe the same or different).

Specific examples that may be cited of compounds having this type offormula include trialkylphosphites such as trimethylphosphite,triethylphosphite, tributylphosphite, trioctylphosphite,tris(2-ethylhexyl)phosphite, trinonylphosphite, tridecylphosphite,trioctadecylphosphite, tristearylphosphite, tris(2-chloroethyl)phosphiteand tris(2,3-dichloropropyl)phosphite; tricycloalkylphosphites such astricyclohexylphosphite; triarylphosphites such as triphenylphosphite,tricresylphosphite, tris(ethylphenyl)phosphite,tris(2,4-di-t-butylphenyl)phosphite, tris(nonylphenyl)phosphite andtris(hydroxyphenyl)phosphite; and arylalkylphosphites such asphenyldidecylphosphite, diphenyldecylphosphite,diphenylisooctylphosphite, phenylisooctylphosphite and2-ethylhexyldiphenylphosphite.

Other examples of phosphites that may be cited includedistearylpentaerythrityldiphosphite andbis(2,4-di-t-butylphenyl)pentaerythrityldiphosphite.

These compounds can be used alone or as combinations thereof.

Of the above, it is desirable that the phosphorus compounds [C] bephosphites having the above formula, preferably aromatic phosphites, andmost preferably tris(2,4-di-t-butylphenyl)phosphite.

These may be added separately and at the same time.

In the present invention, phosphorus compounds [D] such as the above areadded in an amount of 10-1000 ppm, and preferably 50-500 ppm, based onthe polycarbonate [A].

In the present invention, the above-described sulfonic acid compounds[B] and, where necessary, epoxy compounds [C] and/or phosphoruscompounds [D], may be added to the polycarbonate [A] reaction productwhile the polycarbonate [A] is in a molten state, or they they may beadded after remelting polycarbonate [A] that has been pelletized. In theformer case, these are added while the polycarbonate [A] reactionproduct obtained within the reactor or within an extruder followingcompletion of the polycondensation reaction is in a molten state.

More specifically, for example, after polycarbonate has been formed byadding compounds [B] and, if necessary, compounds [C] and [D], to thepolycarbonate [A] obtained by the polycondensation reaction within thereactor, these may be passed through an extruder and pelletized;alternatively, the polycarbonate may be obtained by adding compounds[B], and if necessary compounds [C] and [D], and kneading these whilethe polycarbonate [A] obtained in the polycondensation reaction is beingpassed through an extruder and pelletized.

These various compounds may be added simultaneously or separately. Theorder in which these compounds is added is of no import.

In the present invention, additives such as conventional heatstabilizers, ultraviolet absorbers, parting agents, colorants,antistatic agents, slip agents, anti-blocking agents, lubricants,anti-fogging agents, natural oils, synthetic oils, waxes, organicfillers and inorganic fillers, examples of which are indicated below,may be added to the polycarbonate obtained in the above manner, providedthese do not have adverse effects upon the object of this invention.These additives may be added at the same time as the above compounds[B], [C] and [D], or they may be added separately.

Examples that may be cited of such heat stabilizers include phenol-basedstabilizers, organic thioether-based stabilizers and hinderedamine-based stabilizers.

Specific examples that may be cited of phenol-based stabilizers includen-octadecyl-3(4-hydroxy-3',5'-di-t-butylphenyl)propionate,tetrakis[(methylene-3(3',5'-di-t-butyl-4-hydroxyphenyl)propionate]methane,1,1,3(tris(2-methyl-4-hydroxy-5-t-butylphenyl)butane,distearyl(4-hydroxy-3-methyl-5-t-butyl)benzylmalonate and4-hydroxymethyl-2,6-di-t-butylphenol. These may used alone or asmixtures of two or more thereof.

Examples that may be cited of thioether-based stabilizers includedilauryl thiodipropionate, distearyl thiodipropionate,dimyristyl-3,3'-thiodipropionate, ditridecyl-3,3'-thiodipropionate andpentaerythritol-tetrakis-(β-laurylthiopropionate).

These may be used alone or as mixtures of two or more thereof.

Examples that may be cited of hindered amine-type stabilizers includebis(2,2,6,6-tetramethyl-4-piperidyl)sebacate,bis(1,2,2,6,6-pentamethyl-4-piperidyl)sebacate,1-(2-[3-(3,5-di-t-butyl-4-hydroxyphenyl)propionyloxy]ethyl)-4-[3-(3,5-di-t-butyl-4-hydroxyphenyl)propionyloxy]-2,2,6,6-tetramethylpiperidine,8-benzyl-7,7,9,9-tetramethyl-3-octyl-1,2,3-triazaspiro[4,5]undecane-2,4-dione,4-benzoyloxy-2,2,6,6-tetramethylpiperidine,2-(3,5-di-t-butyl-4-hydroxybenzyl)-2-n-butylmalonic acidbis(1,2,2,6,6-pentamethyl-4-piperidyl) andtetrakis(2,2,6,6-tetramethyl-4-piperidyl)1,2,3,4-butanetetracarboxylate.

These may be used alone or as mixtures of two or more thereof.

These heat stabilizers should be used in an amount of 0.001-5 parts byweight, preferably 0.005-0.5 part by weight, and most preferably0.01-0.3 part by weight, per 100 parts by weight of the polycarbonate[A].

These heat stabilizers may be added in a solid state or in a liquidstate.

It is preferable that this type of heat stabilizer be added while thepolycarbonate [A] is in a molten state during the period when it iscooled and pelletized [after removal] from the final polymerizer; by sodoing, the thermal history incurred by the polycarbonate is small.Moreover, when heating treatment such as extrusion or palletization isagain carried out, thermal decomposition can be suppressed because thepolycarbonate contains a heat stabilizer.

There is no particular restriction on the ultraviolet absorbers used, itbeing possible to use conventional ultraviolet absorbers such assalicylic acid-type ultraviolet absorbers, benzophenone-type ultravioletabsorbers, benzotriazole-type ultraviolet absorbers andcyanoacrylate-type ultraviolet absorbers.

Specific examples of salicylic acid-type ultraviolet absorbers that maybe cited include phenylsalicylate and p-t-butylphenylsalicylate.

Examples that may be cited of benzophenone-type ultraviolet absorbersinclude 2,4-dihydroxybenzophenone, 2-hydroxy-4-methoxybenzophenone,2,2'-dihydroxy-4-methoxybenzophenone,2,2'-dihydroxy-4,4'-dimethoxybenzophenone,2-hydroxy-4-methoxy-2'-carboxybenzophenone,2-hydroxy-4-methoxy-5-sulfobenzophenonetrihydrate,2-hydroxy-4-n-octoxybenzophenone, 2,2',4,4'-tetrahydroxybenzophenone,4-dodecyloxy-2-hydroxybenzophenone,bis(5-benzoyl-4-hydroxy-2-methoxyphenyl)methane, and2-hydroxy-4-methoxybenzophenone-5-sulfonic acid.

Examples that may be cited of benzotriazole-type ultraviolet absorbersinclude 2-(2'-hydroxy-5'-methylphenyl)benzotriazole,2-(2'-hydroxy-3',5'-di-t-butylphenyl)benzotriazole,2-(2'-hydroxy-3'-t-butyl-5'-methylphenyl)-5-chlorobenzotriazole,2-(2'-hydroxy-3,5'-di-t-butylphenyl)-5-chlorobenzotriazole,2-(2'-hydroxy-5'-t-octylphenyl)benzotriazole,2-(2'-hydroxy-3',5'-di-t-amylphenyl)benzotriazole,2-[2'-hydroxy-3'(3",4"5",6"-tetrahydrophthalimidomethyl)-5'-methylphenyl]benzotriazoleand2,2'-methylenebis[4-(1,1,3,3-tetramethylbutyl)-6-(2H-benzotriazole-2-yl)phenol.

Examples that may be cited of cyanoacrylate-type ultraviolet absorbersinclude 2-ethylhexyl-2-cyano-3,3-diphenylacrylate andethyl-2-cyano-3,3-diphenylacrylate. These may be used alone or asmixtures of two or more thereof.

These ultraviolet absorbers can generally be used in an amount of0.001-5 parts by weight, preferably 0.005-1.0 part by weight, and evenmore preferably 0.01-0.5 part by weight, per 100 parts by weight of thepolycarbonate [A].

There is no particular restriction on the parting agents, it beingpossible to use common parting agents.

Examples of hydrocarbon-type parting agents that may be cited includenatural and synthetic paraffins, polyethylene waxes and fluorocarbons.

Examples that may be cited of fatty acid-type parting agents are higherfatty acids such as stearic acid and hydroxystearic acid, and oxyfattyacids.

Examples that may be cited of fatty amide-type parting agents includefatty amides such as stearamide and ethylenebisstearamide, andalkylenebisfatty amides.

Examples that may be cited of alcohol-type parting agents include fattyalcohols such as stearyl alcohol and cetyl alcohol, polyhydric alcohols,polyglycols and polyglycerols.

Examples that may be cited of fatty ester-type parting agents includethe lower alcohol esters of fatty acids such as butyl stearate andpentaerythritol tetrastearate, the polyhydric alcohol esters of fattyacids, and the polyglycol esters of fatty acids.

Examples that may be cited of silicone-type parting agents includesilicone oils. These may be used alone or as mixtures of two or morethereof.

These parting agents can generally be used in an amount of 0.001-5 partsby weight, preferably 0.005-1 part by weight, and most preferably0.01-0.5 part by weight, per 100 parts by weight of the polycarbonate[A].

The colorants may be pigments or dyes. There are both inorganic andorganic colorants, either of which may be used; it is also possible touse combinations of both.

Specific examples that may be cited of inorganic colorants includeoxides such as titanium dioxide and red oxide, hydroxides such asalumina white, sulfides such as zinc sulfide, selenides, ferrocyanidessuch as Prussian blue, chromates such as zinc chromate and molybdenumred, sulfates such as barium sulfate, carbonates such as calciumcarbonate, silicates such as ultramarine blue, phosphates such asmanganese violet, carbons such as carbon black, and metal powdercolorants such as bronze powder and aluminum powder.

Specific examples of organic colorants that may be cited include nitrosocompounds such as naphthol green B, nitro compounds such as naphtholyellow S, azo compounds such as lithol red, bordeaux 10B, naphthol redand chromophthal yellow; phthalocyanine compounds such as phthalocyanineblue and fast sky blue, and condensed polycyclic colorants such asindanthrone blue, quinacridone violet and dioxazine violet.

These colorants may be used alone or as combinations thereof.

These colorants can generally be used in an amount of 1×10⁻⁶ to 5 partsby weight, preferably 1×10⁻⁵ to 3 parts by weight, and most preferably1×10⁻⁵ to 1 part by weight, per 100 parts by weight of the polycarbonate[A].

In this invention, the polycarbonate obtained in the above manner shouldbe administered vacuum treatment.

There is no particular restriction on the apparatus used when carryingout this type of vacuum treatment; for example, a reactor equipped witha vacuum apparatus or an extruder equipped with a vacuum apparatus maybe used.

When a reactor is used, this may be either a vertical tank-type reactoror a horizontal tank-type reactor, although use of a horizontaltank-type reactor is most preferable.

When the vacuum treatment is conducted in the above-described type ofreactor, it is carried out at a pressure of 0.05-750 mmHg, andpreferably 0.05-5 mmHg.

When this kind of vacuum treatment is conducted using an extruder, itshould be carried out over a period of about 10 seconds to 15 minutes.When it is conducted using a reactor, it should be carried out over aperiod of about 5 minutes to 3 hours. The vacuum treatment should becarried out at a temperature of about 240°-350° C.

When the vacuum treatment is carried out in an extruder, a single-screwextruder or twin-screw extruder equipped with a belt may be used.Pelletization can be carried out while conducting vacuum treatment in anextruder.

When vacuum treatment is carried out in an extruder, the vacuumtreatment is carried out at a pressure of 1-750 mmHg, and preferably5-700 mmHg.

When vacuum treatment is administered in this way after the addition topolycarbonate of sulfonic acid compounds [B] and, where necessary, epoxycompounds [C] and phosphorus compounds [D], a polycarbonate wi-.h areduced level of residual monomers and oligomers can be obtained.

The polycarbonate obtained in this invention has a low discolorationimmediately after polycondensation and an excellent residence stabilityat the time of melt molding. Hence, thermal decomposition does notreadily arise during molding; in addition, [the polycarbonate] is notprone to decreases in molecular weight or yellowing, and also has anexcellent hue stability.

Also, in polycarbonate compositions containing epoxy compounds, thewater resistance is improved and the transparency is less apt todecrease.

Because polycarbonates such as these can be formed into moldings havingexcellent long-term hue stability and excellent transparency, broad usecan be made of such polycarbonates, particularly in optical applicationssuch as sheets, lenses and compact disks, in transparent components forautomobiles or the like used outdoors, and also in housings for varioustypes of equipment.

[ADVANTAGES OF THE INVENTION]

In the polycarbonate production method according to the presentinvention, melt polycondensation is carried out by making the alkalimetal compounds and/or alkaline earth metal compounds serving as thecatalyst present in a specific amount within the reaction system andadding specific sulfonic acid compounds to the polycarbonate obtained.

By means of this type of polycarbonate production method according tothe present invention, the polycondensation reaction can be carried outstably while maintaining a high polymerization activity. Moreover, apolycarbonate can be obtained that has an excellent initial color toneimmediately after polycondensation, improved residence stability andwater resistance, and improved heat stability.

Also, it is preferable that epoxy compounds and/or phosphorus compoundsbe added along with these sulfonic acid compounds, thereby making itpossible to obtain polycarbonates having even further improved waterresistances and hue stabilities.

The polycarbonates obtained in this invention have excellent residencestability at the time of melt molding, and are able to form moldingshaving particularly excellent water resistance and transparency.

The present invention shall now be described by means of examples,although the invention shall in no way be restricted by these examples.

[EXAMPLES]

In this specification, the intrinsic viscosity (IV), MFR, hue (YI),light transparency, haze, residence stability and water resistance ofthe polycarbonate were measured as follows.

[Intrinsic Viscosity (IV)]

This was measured at 20° C. in methylene chloride using an Ubbelohdeviscometer.

[MFR]

This was measured at a temperature of 300° C. and a load of 1.2 kg ingeneral accordance with the method in JIS K-7210.

[Yellowness]

An injection-molded sheet having a thickness of 3 mm was molded at acylinder temperature of 290° C., an injection pressure of 1000 kg/cm², acycle time of 45 seconds, and a mold temperature of 100° C. The X, Y andZ values were measured by the transmission method using a Color andColor Difference Meter ND-1001 DP made by Nippon Denshoku Kogyo KK, andthe yellow index (YI) was measured.

    YI=100(1.277X-1.060Z)/Y

[Light Transmittance]

Using the injection molded sheet prepared for hue measurement, the lighttransmittance was measured in accordance with the method in ASTM D 1003.

[Haze]

The haze of the injection-molded sheet for hue measurement was measuredusing an NDH-200 made by Nippon Denshoku Kogyo KK.

[MFR]

The MFR was measured at a temperature of 300° C. and a load of 1.2 kg,in general accordance with the method in JIS K-7210

[Residence Stability]

After retaining the resin within the cylinder of the injection moldingmachine for 15 minutes at a temperature of 320° C., injection moldingwas carried out at that temperature, and the MFR, hue (YI) and lighttransmittance of the molded sheet were measured.

[Water Resistance]

The injection-molded sheet for hue measurement was immersed in waterwithin an autoclave, and held for 5 days in an oven at 125° C. The hazewas measured using this test piece.

[Elemental Analysis]

Quantitative determinations of alkali metal e and alkaline earth metalswere carried out on 100-mg samples using a flameless atomic absorptionspectroscopic analyzer (model TSC-10; Mitsubishi Kasei Corp.)

[EXAMPLES]

An elemental analysis of bisphenol A (GE Plastics Japan) was conducted,from which the combined level of alkali metals and of alkaline earthmetals was found to be less than 1 ppb; hence, this was used directly asa starting material.

The diphenyl carbonate ("Enii"* Co.) was purified by distillation; thiswas used as a starting material after the amount of alkali metals andalkaline earth metals was confirmed to be less than 1 ppb.

A 20% aqueous solution of tetramethylammonium hydroxide (Toyo Gosei) wasused as a starting material after the level of alkali metals andalkaline earth metals was confirmed to be less than 1 ppb.

[Example 1]

After charging a 250-liter tank-type stirring tank with 0.44 kilomole ofbisphenol A and 0.46 kilomole of diphenyl carbonate, and flushing thetank with nitrogen, [the mixture] was melted at 140° C.

Next, the temperature was raised to 180° C., 0.000176 mole (4×10⁻⁷mole/mole of hisphenol A) cf sodium hydroxide and 0.11 mole (2.5×10⁻⁴mole/mole of bisphenol A) were added as the catalyst, and [the mixture]was stirred for 30 minutes.

The temperature was then raised to 210° C. and the pressure was at thesame time gradually lowered to 200 mmHg; 30 minutes later, thetemperature was raised To 240° C. and the pressure was simultaneouslylowered gradually to 15 mmHg, after which both temperature and pressurewere held constant and the amount of phenol distilled off was measured.At the point in time at which the phenol stopped being driven off, thepressure was returned to atmospheric pressure with nitrogen. The timerequired for reaction was one hour. The intrinsic viscosity [η] of thereaction product was 0.15 L/g.

Next, this reaction product was pressurized with a gear pump and sentinto a centrifugal thin-film evaporator, where the reaction was allowedto proceed. The temperature and pressure of the thin-film evaporatorwere respectively controlled to 270° C. and 2 mmHg. [The reactionproduct] was sent by means of a gear pump from the bottom of theevaporator into a two-shaft lateral-type stirring polymerization tank(L/D t 3; stirring element rotational diameter, 220 ram; capacity. 80liters) controlled to 293° C. and 0.2 mmHg at a rate of 40 kg/hour, andpolymerized at a residence time of 30 minutes.

Next, this polymer was sent in a molten state by means of a gear pumpinto a twin-screw extruder (L/D=17.5; barrel temperature, 285° C). Thiswas kneaded with 0.7 ppm of butyl p-toluenesulfonate, after which it waspassed through a die and formed into strands. then cut so as to givepellets.

The intrinsic viscosity (IV) of the polymer thus obtained was 0.49 dL/g.

The results are shown in Table 1.

[Example 2]

Pellets were obtained by the same method as in Example 1, except that300 ppm of 3,4-epoxycyclohexyl-methyl-3',4'-epoxycyclohexylcarboxylate("Celoxide" 2021P; Daicel Chemical Industries) was added along with the0.7 ppm of butyl p-toluenesulfonate.

The results are shown in Table 1.

[Example 3]

Pellets were obtained by the same method as in Example 1, except that300 ppm of 3,4-epoxycyclohexyl-methyl-3',4'-epoxycyclohexylcarboxylate("Celoxide" 2021P; Daicel Chemical Industries) and 300 ppm oftris(2,4-di-t-butylphenyl)phosphite ("Mark" 2112: "Adeka Argas" Co.)were added along with the 0.7 ppm of butyl p-toluenesulfonate.

The results are shown in Table 1.

[Examples 4-12]

Pellets were obtained by the same method as in Example 1, aside from theuse of the catalysts and additives in Table 1 in the indicated amounts,and aside from setting the final polymerization temperature at 290° C.in Examples 4-6, and at 289° C. in Examples 7-9.

The results are shown in Table 1.

[Example 13]

Pellets were obtained by the same method as in Example 1, except thattetramethylammonium hydroxide was not used, and the reaction was carriedout at 180° C. for 2 hours and at 210° C. for 1 hour.

[Reference Examples 1-8]

Pellets were obtained by the same method as in Example 1, aside from theuse of the catalysts and additives in Table 1 in the indicated amounts,and aside from setting the final polymerization temperature at 287° C.in Reference Examples 1-3, at 285° C. Reference Example 4, at 282° C. inReference Example 5, at 293° C. in Reference Example 7, and at 280° inReference Example 8.

The results are shown in Table 1.

In Reference Example 6, the final temperature of reactor was raised to310° C. and the polycondensation reaction was carried out, but themolecular weight (intrinsic viscosity [η] temperature) did not rise tothe target level.

                  TABLE 1                                                         ______________________________________                                                     Example  Example  Example                                                                              Example                                              1        2        3      4                                       ______________________________________                                        Catalyst                                                                      1) NaOH      4.0      4.0      4.0    6.0                                     amount, 10.sup.-7                                                             mol/BPA)                                                                      2) Me.sub.4 NOH                                                                            2.5      2.5      2.5    2.5                                     amount (10.sup.-4                                                             mole/BPA)                                                                     Additive                                                                      [B] Compound BTS      BTS      BTS    BTS                                     (amount used, ppm)                                                                         0.7      0.7      0.7    1.1                                     [C] Epoxy Compound                                                                         --       2021P    2021P  --                                      (amount used, ppm)                                                                         --       300      300    --                                      [D] Phosphorus                                                                             --       --       TDBPP  --                                      Compound                                                                      (amount used, ppm)                                                                         --       --       300    --                                      Initial properties                                                            IV (dL/g)    0.49     0.49     0.49   0.49                                    YI           1.41     1.41     1.40   1.44                                    Light        90.9     90.9     90.9   90.9                                    transmittance (%)                                                             Haze         0.2      0.2      0.2    0.2                                     MFR (g/10 min)                                                                             10.4     10.3     10.4   10.5                                    Residence stability                                                           YI           1.51     1.52     1.41   1.54                                    MFR (g/10 min)                                                                             10.6     10.5     10.6   10.8                                    MFR rise (%) 2        2        2      3                                       Water resistance                                                              Haze         0.6      0.5      0.8    0.9                                                  (C, T, TC)                                                                             (C, T, NC)                                                                              (C, T, NC)                                                                          (C, T, TC)                              ______________________________________                                                     Example  Example  Example                                                                              Example                                              5        6        7      8                                       ______________________________________                                        Catalyst                                                                      1) NaOH      6.0      6.0      7.0    7.0                                     amount, 10.sup.-7                                                             mol/BPA)                                                                      2) Me.sub.4 NOH                                                                            2.5      2.5      2.5    2.5                                     amount (10.sup.-4                                                             mole/BPA)                                                                     Additive                                                                      [B] Compound BTS      BTS      BTS    BTS                                     (amount used, ppm)                                                                         1.1      1.1      1.3    1.3                                     [C] Epoxy Compound                                                                         2021P    2021P    --     2021P                                   (amount used, ppm)                                                                         300      300      --     300                                     [D] Phosphorus                                                                             --       TDBPP    --     --                                      Compound                                                                      (amount used, ppm)                                                                         --       300      --     --                                      Initial properties                                                            IV (dL/g)    0.49     0.49     0.49   0.49                                    YI           1.44     1.43     1.49   1.49                                    Light        90.9     90.9     90.9   90.9                                    transmittance (%)                                                             Haze         0.2      0.2      0.2    0.2                                     MFR (g/10 min)                                                                             10.4     10.4     10.3   10.3                                    Residence stability                                                           YI           1.55     1.45     1.59   1.59                                    MFR (g/10 min)                                                                             10.6     10.6     10.5   10.5                                    MFR rise (%) 2        2        2      2                                       Water resistance                                                              Haze         0.7      1.0      1.0    0.9                                                  (C, T, NC)                                                                             (C, T, NC)                                                                              (C, T, TC)                                                                          (C, T, NC)                              ______________________________________                                                     Example  Example  Example                                                                              Example                                              9        10       11     12                                      ______________________________________                                        Catalyst                                                                      1) NaOH      7.0      4.0      4.0    4.0                                     amount, 10.sup.-7                                                             mol/BPA)                                                                      2) Me.sub.4 NOH                                                                            2.5      2.5      2.5    2.5                                     amount (10.sup.-4                                                             mole/BPA)                                                                     Additive                                                                      [B] Compound BTS      TS       TS     TS                                      (amount used, ppm)                                                                         1.3      0.5      0.5    0.5                                     [C] Epoxy Compound                                                                         2021P    --       2021P  2021P                                   (amount used, ppm)                                                                         300      --       300    300                                     [D] Phosphorus                                                                             TDBPP    --       --     TDBPP                                   Compound                                                                      (amount used, ppm)                                                                         300      --       --     300                                     Initial properties                                                            IV (dL/g)    0.49     0.49     0.49   0.49                                    YI           1.48     1.41     1.41   1.40                                    Light        90.9     90.9     90.9   90.9                                    transmittance (%)                                                             Haze         0.2      0.2      0.2    0.2                                     MFR (g/10 min)                                                                             10.4     10.3     10.3   10.3                                    Residence stability                                                           YI           1.49     1.50     1.51   1.42                                    MFR (g/10 min)                                                                             10.6     10.5     10.5   10.5                                    MFR rise (%) 2        2        2      2                                       Water resistance                                                              Haze         1.1      0.7      0.7    0.9                                                  (C, T, NC)                                                                             (C, T, TC)                                                                             (C, T, NC)                                                                           (C, T, NC)                              ______________________________________                                                           Example 13                                                 ______________________________________                                        Catalyst                                                                      1) NaOH            4.0                                                        amount, 10.sup.-7 mol/BPA)                                                    2) Me.sub.4 NOH    --                                                         amount (10.sup.-4 mole/BPA)                                                   Additive                                                                      [B] Compound       BTS                                                        (amount used, ppm) 0.7                                                        [C] Epoxy Compound --                                                         (amount used, ppm) --                                                         [D] Phosphorus Compound                                                                          --                                                         (amount used, ppm) --                                                         Initial properties                                                            IV (dL/g)          0.49                                                       YI                 1.41                                                       Light transmittance (%)                                                                          90.9                                                       Haze               0.2                                                        MFR (g/10 min)     10.4                                                       Residence stability                                                           YI                 1.52                                                       MFR (g/10 min)     10.6                                                       MFR rise (%)       2                                                          Water resistance                                                              Haze               0.7                                                                           (C, T, NC)                                                 ______________________________________                                                     Refer-   Refer-   Refer- Refer-                                               ence     ence     ence   ence                                                 Example  Example  Example                                                                              Example                                              1        2        3      4                                       ______________________________________                                        Catalyst                                                                      1) NaOH      10.0     10.0     10.0   20.0                                    amount, 10.sup.-7                                                             mol/BPA)                                                                      2) Me.sub.4 NOH                                                                            2.5      2.5      2.5    2.5                                     amount (10.sup.-4                                                             mole/BPA)                                                                     Additive                                                                      [B] Compound BTS      BTS      BTS    BTS                                     (amount used, ppm)                                                                         1.8      1.8      1.8    3.5                                     [C]  Epoxy Compound                                                                        --       2021P    2021P  2021P                                   (amount used, ppm)                                                                         --       300      300    300                                     [D] Phosphorus                                                                             --       --       TDBPP  TDBPP                                   Compound                                                                      (amount used, ppm)                                                                         --       --       300    300                                     Initial properties                                                            IV (dL/g)    0.49     0.49     0.49   0.49                                    YI           1.67     1.68     1.54   1.86                                    Light        90.8     90.8     90.8   90.8                                    transmittance (%)                                                             Haze         0.2      0.2      0.2    0.2                                     MFR (g/10 min)                                                                             10.3     10.4     10.5   10.4                                    Residence stability                                                           YI           1.85     1.89     1.64   1.98                                    MFR (g/10 min)                                                                             11.0     11.2     11.2   11.3                                    MFR rise (%) 7        8        7      9                                       Water resistance                                                              Haze         5.4      4.2      5.3    11.3                                                 slightly slightly slightly                                                                             slightly                                             cloudy   cloudy   cloudy cloudy                                  ______________________________________                                                     Refer-   Refer-   Refer- Refer-                                               ence     ence     ence   ence                                                 Example  Example  Example                                                                              Example                                              5        6        7      8                                       ______________________________________                                        Catalyst                                                                      1) NaOH      40.0     0.2      4.0    50.0                                    amount, 10.sup.-7                                                             mol/BPA)                                                                      2) Me.sub.4 NOH                                                                            2.5      2.5      2.5    2.5                                     amount (10.sup.-4                                                             mole/BPA)                                                                     Additive                                                                      [B] Compound BTS      BTS      BTS    BTS                                     (amount used, ppm)                                                                         7.0      0.1      15.0   100.0                                   [C] Epoxy Compound                                                                         2021P    --       --     --                                      (amount used, ppm)                                                                         300      --       --     --                                      [D] Phosphorus                                                                             TDBPP    --       --     --                                      Compound                                                                      (amount used, ppm)                                                                         300      --       --     --                                      Initial properties                                                            IV (dL/g)    0.49     0.28     0.49   0.49                                    YI           2.10     NM       1.42   2.90                                    Light        90.7     --       90.9   90.7                                    transmittance (%)                                                             Haze         0.3      --       0.2    0.3                                     MFR (g/10 min)                                                                             10.3     >100     10.4   10.3                                    Residence stability                                                           YI           2.43     --       1.65   3.15                                    MFR (g/10 min)                                                                             12.1     --       10.9   11.4                                    MFR rise (%) 17       --       5      11                                      Water resistance                                                              Haze         83.4     --       93     98                                                   cloudy   --       cloudy cloudy                                  ______________________________________                                         BTS = butyl ptoluenesulfonate;                                                2021P = "Celoxide" 2021P                                                      TS = ptoluenesulfonic acid;                                                   TDBPP = tris(2,4di-t-butylphenyl)phosphite;                                   C = colorless;                                                                T = transparent;                                                              TC = tiny cracks;                                                             NC = no cracks)                                                               NT = not moldable                                                        

We claim:
 1. A method for preparing polycarbonates, which methodcomprises inducing the melt polycondensation of an aromatic dihydroxycompound and a diester carbonate in the presence of a total amount inthe reaction system of 5×10⁻⁸ to 8×10⁻⁷ mole of alkali metal compoundsor alkaline earth metal compounds per mole of the aromatic dihydroxycompound, and adding to the polycarbonate which is the reaction productthereof:a sulfonic acid compound having the formula ##STR7## where R⁷ isa hydrocarbon group having 1-6 carbons in which the hydrogens may besubstituted with halogens R⁸ is a hydrocarbon group with 1-8 carbons inwhich the hydrogens may be substituted with halogens and n is an integerfrom 0 to 3 in an amount of 0.05-10 ppm, based on the polycarbonate, andan epoxy compound in an amount of 1-2000 ppm, based on thepolycarbonate.
 2. A method for preparing polycarbonates according toclaim 1, whereby the epoxy compound [C] is used in an amount of 1-1000ppm, based on the polycarbonate.
 3. A method for preparingpolycarbonates according to claim 1, whereby the epoxy compound [C] isan alicyclic epoxy compound.
 4. A method for preparing polycarbonatesaccording claim 1, whereby the epoxy compound [C] is3,4-epoxy-cyclohexylmethyl-3',4'-epoxycyclohexylcarbonate.